Top drives are commonly used in the oil and gas industry for rotating drill pipe during drilling operations. The top drive is generally arranged in a drilling rig, and is raised and lowered using a hoisting system, such as a drawworks arrangement. The top drive comprises motors, for example, electric or hydraulic motors, to provide rotational torque on the drill string.
Top drives are subject to high operational demands. The top drive is usually subjected to very high forces in use due to the high torques required during drilling and the large weight of the drill string. The top drive will also experience large load variations during the repeated connect/disconnect sequences when adding or removing sections of pipe to the drill string, and it may also be subject to very high adverse loads such as vibrations or other forces extending upwards through the drill string, for example, during jarring events. Top drives therefore require periodic inspection and maintenance.
Related prior art which is useful for understanding the design and use of conventional top drive systems includes: US 2008/135228 A1; US 2006/113084 A1; U.S. Pat. No. 5,388,651 A; EP 0747567 A2; EP 0712992 A2; US 2007/074874 A1; US 2008/099221 A1; US 2008/238095 A1; US 2006/113087 A1; U.S. Pat. Nos. 3,768,579 A; 4,667,752 A; 7,055,594 B1; 5,433,279 A; 6,276,450 B1; US 2005/269104 A1; US 2005/173154 A1; U.S. Pat. Nos. 4,753,300 A; and 4,878,546 A.
A continuous need exists for improved systems and methods in relation to top drive operation and maintenance, in particular in light of the tendency of the industry to move into harsher and more challenging areas, for example, deepwater resources or arctic areas. This includes solutions for improving reliability and for simplifying maintenance of the top drive and its various components.